Internal threading tool Question

[fishingreg]

I have several different internal threading tools, every one but this one the tool flats for the holder parallel with cutting edge of the tool so the cutting edge hits the material at 90 degrees. This one is angled down from the flats on the tool so when I clamp it into the tool holder it is angled down. It is a cheap tool but I still I don't understand the angle. Has anyone seen a threading tool angled like this? In the picture I could not get the flats and the cutting edge all in the same pic where you could see it good so I just showed the angle of the cutting edge but the tool is sitting on its flat as it would in a tool holder. Maybe it should be like this but it does not make sense to me but I'm fairly new to lathe work, any thoughts would be appreciated.

 

[mikey]

That is a LH threading tool so you would use it on the back wall, in reverse. Despite the angle of the insert, the cutting edge is oriented correctly so it would work.

 

[Buffalo21]

Yep, I use it to be able see what I’m doing, when threading to stop or ridge. Much easier to see the tool on the backside.

 

[bakrch]

If the insert was laid flat, and relief (for diametral clearance )was ground to said flat insert, this tool would chip very easily.

What you have here is a more robust geometry.

 

[fishingreg]

Thanks All,

I probably should have mentioned it was left handed, I do thread in reverse to make it easy for me but I typically use Micro-100 tools and they are all 90 degrees to the work piece and not angled like this so I was a bit scared to use it. I appreciate the help and I will give it a run, I just thought something might have been made incorrectly since it was a cheap tool. I have a boring bar that is about the same angle so I assume that one is ok as well now. I was avoiding those 2 until I knew more. Thank you all very much.

 

[mikey]

Boring bars are different. If you have a boring bar with a negative rake angle it will be more difficult to bore with precision because negative rake tools really increase cutting forces. You are far better off using positive rake geometry for boring tools.

 

[bakrch]

Boring bars are different. If you have a boring bar with a negative rake angle it will be more difficult to bore with precision because negative rake tools really increase cutting forces. You are far better off using positive rake geometry for boring tools.

He could also just use a ground edge insert with a chip breaker that is aggressive enough to cancel out the negative rake.

 

[benmychree]

It is not negative rake, it is neutral rake, the top of the cutting part of the too, is radial (like most all threading tools; If the insert was on the center line, the boring bar seat at the bottom would have to be quite thin, lacking shear strength.

 

[mikey]

It is not negative rake, it is neutral rake, the top of the cutting part of the too, is radial (like most all threading tools; If the insert was on the center line, the boring bar seat at the bottom would have to be quite thin, lacking shear strength.

We are talking about boring bars here and I am saying if the tool's cutting edge is forward of center then it is, in effect, negative rake.

 

[mikey]

He could also just use a ground edge insert with a chip breaker that is aggressive enough to cancel out the negative rake.

I admit that I basically ignore negative rake boring bars as they are not useful to me as a hobby guy but can you tell me which bar and insert you're referring to? There are turning tools that can be configured this way but with the deflection a boring bar sees I haven't seen such a combination and it might be interesting to have a look at the geometry.